In a previous study, protein feeding, which normally increases urinary dopamine without a change in plasma DOPA, was shown to increase plasma DOPA when DOPA decarboxylase was inhibited. These observations led to the conclusion that protein feeding increased the delivery of DOPA to the kidney, thereby increasing renal formation of dopamine. Since an increase in sodium intake also stimulates renal formation of dopamine, the possibility that it does so through changes in DOPA metabolism was studied. When sodium intake was decreased from 109 to 9 mEq/day in normal subjects on a constant metabolic diet, renal clearance and excretion of DOPA decreased. When sodium intake was increased from 9 to 249 mEq/d, renal clearance and excretion of DOPA increased by 82% and 62% respectively; the excretion of dopamine increased by 23%. The changes in renal clearance of DOPA occurred without a change in plasma DOPA. The results are consistent with the interpretation that changes in sodium intake may affect renal dopamine formation by altering DOPA metabolism and, in turn, its delivery to the kidney.